The present invention relates to a cold storage body for cooling foods and pharmaceuticals and the like in a refrigerator or a refrigerator car in which no thermodynamically operated refrigerating machine is provided.
Heretofore, as a cold storage body of the kind described above, a cooling medium rendered to be in the state of ice or dry ice by removing heat from the cooling medium which is kept in the liquid or gaseous state at the normal temperature is used in the loose state or in bulk, or two kinds of substances are used which are stored in separate places from each other, and they are mixed with each other for cooling by virtue of the chemical reaction thereof so as to generate cold.
One well known cold storage body comprises in general a viscous cold storage medium hermetically sealed in a soft or rigid plastic vessel. Such a cold storage body has the following difficulties due to the nature of the plastic vessel.
(a) Since the thermal conductivity of the plastic vessel is low, a long time is required for freezing the cold storage medium contained in the plastic vessel, and the cooling effect obtained by the cold storage medium is rather slow. Therefore a, large number of cold storage bodies must be prepared in order to insure positive cooling of the goods, because the time required for freezing the cold storage bodies is too long.
(b) The soft or thin plastic vessels are liable to be damaged or broken and the durability of such vessles is low. Further, as a common difficulty inherent in the vessels made of plastic material, climate resisting property or temperature and humidity resisting property and light or radiation resistance of such vessels are low and they are prone to aging and change in quality so that their useful life is short.
(c) Since the plastic material shrinks or becomes brittle with cold, vessels made of plastic material can not be used in the low temperature range such as -15.degree. C.--25.degree. C. Further, it has disadvantages in achieving rapid freezing of the cold storage medium therein at a low temperature.
(d) A plastic vessel is liable to be soiled and difficulties arise in washing and sterilization with hot water, because the vessel is softened by hot water.
(e) With a soft plastic vessel, the outer shape of the vessel easily varies and is unstable even though a cold storage medium in the gelled state is used, and, therefore, use thereof is not convenient.